As one skilled in the medical field appreciates, it is unacceptable to use any medical instrument that would interfere with the magnetic field of a magnetic resonance imaging machine (MRI). As is well known, the MRI utilizes an external magnetic field that is created by a series of electromagnets in a scanner that serve to excite the hydrogen atoms in the body of the patient being analyzed. These hydrogen atoms create radio signals which are read by a computer and converted into detailed images. This invention addresses this problem by providing a pneumatic motor that is capable of being used in the presence of an MRI machine without adversely affecting the magnetic field generated thereby and hence, is incapable of adversely affecting the image generated by this machine. In addition, as will be more fully explained hereinbelow, this invention also provides improvements to heretofore known pneumatic surgical motors notwithstanding the fact that these prior art motors are not usable in an MRI environment. In other words, this invention applies to pneumatic surgical motors that can be used with MRI machines and to those motors that cannot be used with MRI machines. Obviously, a motor that can be used with an MRI machine can also be used where an MRI machine is not being used.
This invention contemplates the improvement of heretofore known pneumatic surgical motors including the pneumatic surgical motors being manufactured by and sold by the assignee and all are well known in the medical industry as the Black Max, the Micro Max and the Micro Max Plus and all of which are incorporated herein by reference. While these motors mentioned immediately above in this paragraph are not capable of use with MRI machines, this invention provides all of the features that are associated with these motors, but does so with an improved surgical instrument. For example, the Black Max is a heavy duty motor that is more powerful and larger than the other two motors, but is heavier, hotter, noisier and vibrates more than these other motors. The Micro Max, supra, was developed to reduce the size, noise, vibration and heat and to be essentially more gentle for use by the surgeon and likewise, has developed a niche in the industry. Obviously, the power is reduced. However, this motor for some medical procedures does not meet the needs of the surgeons because it lacked the necessary power which gave rise to the Micro Max Plus motor, which, again, has more power than the Micro Max but, yet, less power than the Black Max. The Micro Max Plus falls in the category of being more gentle for use by the surgeon but again, because of the increased power, heat, vibrations and weight of the Micro Max Plus (higher than the Micro Max but still lower than the Black Max) it, likewise, has gained a niche in the industry. A more technical way of looking at each of these motors is that the length of the cylinder supporting the vanes of the each of the motors are increased as a function of the power generated, namely, the lengths of the cylinders of the Black Max=1.0 inch (″), the Micro Max=¾″ and the Micro Max Plus=½″. It is reasonable to state that each of these motors served a particular need for a particular surgeon doing a particular operation or medical procedure on a patient.
As one skilled in this technology will appreciate, the outside diameter of all of the well known commercially available pneumatic surgical motors including the ones noted in the above paragraphs are substantially equal and include a rotor that is driven by pressurized air for rotating a spindle that is rotatably supported by bearings in an outer housing that serves as the handle of the motor. All of these motors also include in some form or another the necessary seals, anti-rotational device, inlet and outlet for the pressurized air and means for lubricating the bearings and their support structures or internal housings.
We have found that we can provide an improved pneumatic surgical motor that satisfies the requirements of all the functions of the three motors that are discussed in the above paragraphs, but is an improvement there over while providing higher power with a smaller cylinder than the one in the Black Max, is lighter than the smallest of these motors, is cooler, exhibits less vibrations, is quieter and is as gentle to handle as is the smallest of these three motors. These improvements are not only germane to the motors manufactured by the assignee, but are improvements to heretofore known competitive motors.
The following aspects of this invention to be discussed immediately below which are not to be construed as limitations thereto, contribute to the overall improvements to the inventive motor. . . .                1. Utilize spindle bearings with alternating metal and plastic needles.        2. Zero velocity axial thrust support for minimizing wear and lower heat.        3. Laminated seal for lower velocity and lower heat.        4. Increased vane working surface for augmenting the power of the motor.        5. Angled slots formed on the spindle to enhance power of the motor and minimizes wear by discretely.        6. Spindle end thrust bearings to prevent metal-to-metal on outward exerted axial thrust.        7. Exhaust holes formed on the cylinder discharging compressed air are judiciously located to minimize wear on the edge of the vane by distributing contact area evenly and to reduce noise of the motor.        8. Cylindrical holes for the input air to the vane motor so as to increase air volume.        9. Cylinder crescent seal to increase the effectiveness of the spindle-to-cylinder gap seal and minimize lubrication requirements.        10. Stainless steel housing and isolation peek sleeve.        11. Increased power cycle by increasing the circumferential spacing between the vane motor's inlet and outlet ports.        12. Noise reduction by crisscrossing outlet air flow.        13. Slots in the cylinder formed adjacent to the inlet holes for directing air cool over the cylinder before entering the vane motor.        